Method of making a semifinished product

ABSTRACT

A semifinished product for making a composite fiber molded part is made by first spinning from a row of orifices of a spinning nozzle low-melting fibers of a thermoplastic. These low-melting fibers are then combined into a laminated semifinished product with high-melting reinforcement fibers of the same thermoplastic but having a melting temperature higher than the melting temperature of the low-melting fibers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application a division of U.S. patent application Ser. No.14/428,004 filed 13 Mar. 2015 as the US-national stage of PCTapplication PCT/EP2013/070579 filed 2 Oct. 2013 and claiming thepriority of European patent application 12186973.9 itself filed 2 Oct.2012.

FIELD OF THE INVENTION

The invention relates to a method of making a semifinished product formaking a composite molded part, in particular a composite fiber moldedpart. The invention further relates to a semifinished product for makingsuch a composite molded part, in particular a composite fiber moldedpart. Furthermore the invention also relates to a composite molded part,in particular a composite fiber molded part. The invention relatesespecially to composite molded parts or composite fiber molded parts asa lightweight construction.

BACKGROUND OF THE INVENTION

The term “composite molded part” means that reinforcement material ornon-molten reinforcement material is embedded in a matrix ofthermoplastic plastic. The term “composite fiber molded part” means thatfibers or non-molten fibers are present in the composite molded part orin the matrix of thermoplastic plastic. The composite molded parts orcomposite fiber molded parts produced according to the invention can onthe one hand have a two-dimensional form, in particular the shape of aplate or the like. The composite molded parts or composite fiber moldedparts produced according to the invention preferably have athree-dimensional shape.

Methods, semifinished products and composite molded parts of the typereferred to above are already known in the art in different embodiments.In the known methods, first of all semifinished products are producedthat consist of a matrix of thermoplastic plastic and reinforcementfibers embedded therein. To this end the reinforcement fibers—forexample glass fibers—are first of all combined with films, powders,fibers or melts of thermoplastic plastic. The thermoplastic plastic ismelted by the application of heat and pressure and in this way thereinforcement fibers are impregnated with the melt, ultimately resultingin the semifinished product made of the thermoplastic matrix with theembedded reinforcement fibers. These semifinished products are alsoknown as organic sheets and they are generally produced in the form ofplates. For making a composite fiber molded part with athree-dimensional shape the plates must be heated again in a lateradditional processing step before they can be formed into the requiredcomposite fiber molded part. The known methods and semifinished productshave a number of disadvantages. First of all in the manufacture ofsemifinished products—in particular when films of thermoplastic plasticare used—the extent of the penetration or impregnation of thereinforcement fibers with the thermoplastic plastic leaves something tobe desired. Furthermore air inclusions are frequently produced and as aresult weak points are created in the composite molded part or compositefiber molded part that is produced. Moreover, the semifinished productsthat are produced are often characterized by insufficient drapingproperties. Therefore the manufacture of three-dimensional ormulti-dimensional composite molded parts or composite fiber molded partsis subject to limitations. Furthermore the recycling of known fibercomposite materials is difficult when a thermoplastic matrix isreinforced with reinforcement fibers that are inorganic or difficult tomelt. Moreover the recycling of thermosetting plastics is also difficultand costly in the case of composite molded parts or composite fibermolded parts produced according to the known measures.

OBJECT OF THE INVENTION

On the other hand the object of the invention is to provide a method ofthe type referred to above, where the previously described disadvantagescan be avoided in an effective and functionally reliable manner.Furthermore another object of the invention is to provide a semifinishedproduct for the manufacture of a composite molded part or compositefiber molded part as well as a corresponding composite molded part orcomposite fiber molded part.

SUMMARY OF THE INVENTION

In order to attain these objects, the invention proposes a method ofmaking a semifinished product for the manufacture of a composite moldedpart, in particular a composite fiber molded part, wherein ahigh-melting reinforcement material, in particular high-meltingreinforcement fiber is combined with low-melting fibers made ofthermoplastic plastic into a laminate, wherein the low-melting fibersare spun and are combined at a fiber temperature T_(F) with thehigh-melting reinforcement material, in particular with the high-meltingreinforcement fibers into the laminate forming the semifinished product,wherein the fiber temperature T_(F) lies in a temperature range betweena temperature of 25° C. below the heat distortion\temperature T_(W) to55° C. above the heat-distortion temperature T_(W) of the thermoplasticplastic of the low-melting fibers. Thus the following applies: T_(W)−25°C.≤T_(F)≤T_(W)+55° C. It is within the scope of the invention that thefiber temperature T_(F) is lower than the melting temperature of thethermoplastic plastic of the low-melting fibers. It is also within thescope of the invention that the low-melting fibers are spun and afterthe spinning are combined at a fiber thickness <10 den, preferably <3den and particularly preferably <1.5 den and at the fiber temperatureT_(F) with the high-melting reinforcement material, in particular withthe high-melting reinforcement fibers, into the laminate forming thesemifinished product.

Within the scope of the invention “high-melting” means that thehigh-melting component has a higher melting point than the low-meltingcomponent, the two melting points being determined under the sameexternal conditions. Within the scope of the invention high-meltingreinforcement material also encompasses non-melting reinforcementmaterial and accordingly within the scope of the invention the term“high-melting reinforcement fibers” also encompasses non-meltingreinforcement fibers. These reinforcement fibers—for example carbonfibers—generally disintegrate at very high temperatures. It isrecommended that the reinforcement material and in particular thereinforcement fibers are used as laid fabric and/or woven fabric and/orbraided fabric and/or knitted fabric and/or meshes or the like. Apreferred embodiment is characterized in that at least one laid fabricand/or at least one woven fabric made of reinforcement fibers forms/formthe at least one layer of high-melting reinforcement fibers. Within thescope of the invention high-melting foams or honeycombs can be used ashigh-melting reinforcement material. It is within the scope of theinvention that the melting point of the high-melting reinforcementmaterial or the high-melting reinforcement fibers is at least 1° C.,preferably at least 5° C. higher than the melting point of thelow-melting fibers. According to an embodiment of the invention themelting point of the high-melting reinforcement material or thehigh-melting reinforcement fibers is at least 20°, preferably at least30° C. and preferably at least 50° C. higher than the melting point ofthe low-melting fibers.

According to the invention the fiber temperature T_(F) of thelow-melting fibers in their combination with the reinforcement materialor with the reinforcement fibers in the range specified there is lowerthan the heat-distortion temperature T_(W) or in the range specifiedthere is higher than the heat-distortion temperature T_(W) of thethermoplastic plastic of the low-melting fibers. Naturally it can alsocorrespond to the heat-distortion temperature T_(W). The fibertemperature T_(F) of the low-melting fibers in the event of theplacement or in combination with the reinforcement material may bemeasured as process temperature or air temperature in the placement orcombination of the low-melting fibers in the current method. The heatdistortion or the heat-distortion temperature T_(W) of the thermoplasticplastic of the low-melting fiber is a measure of the temperaturestability of this thermoplastic plastic. The heat-distortion temperaturecan be measured according to DIN EN ISO 75-2:2004, method B (heatingrate 50 K/h) on an untempered test piece.

A particularly preferred embodiment of the method according to theinvention is characterized in that the fiber temperature T_(F) of thelow-melting fibers in combination with the reinforcement material liesbetween a temperature T_(F) of 20° C.—preferably 15° C.—below theheat-distortion temperature T_(W) to 50° C.—preferably 45° C.—above theheat-distortion temperature T_(W) of the thermoplastic of thelow-melting fibers. As already demonstrated above, however, it is withinthe scope of the invention that the fiber temperature T_(F) lies belowthe melting point of the thermoplastic plastic of the low-meltingfibers.

Advantageously in the method according to the invention, after thespinning, the low-melting fibers are continuously delivered to thereinforcement material or the reinforcement fibers. In this case thelow-melting fibers preferably retain the fiber temperature T_(F) fromthe heating in the spinning operation. Thus it is recommended that atreatment or cooling of the low-melting fibers only takes place to theextent that according to the invention the fiber temperature T_(F)according to the invention lies in the range specified there. It iswithin the scope of the invention that the reinforcement material hasinterstices or that between the reinforcement fibers interstices areformed and that during the combination of the low-melting fibers withthe reinforcement material or with the reinforcement fibers the fibersor the fiber sections of the low-melting fibers can penetrate into theinterstices. In this respect the invention is based on the recognitionthat the low-melting fibers combined according to the invention with thereinforcement material with the reinforcement fibers with the fibertemperature T_(F) are sufficiently flexible or malleable or soft thatthey can penetrate into the interstices of the reinforcement material orbetween the reinforcement fibers without problems at least with fibersections. This results in a sort of entanglement of the reinforcementmaterial or the reinforcement fibers with the low-melting fibers.Furthermore the invention is based on the recognition that the laminateproduced in the manner described above is sufficiently stable andconsistent in shape or is already sufficiently consolidated, so that itcan be delivered directly to the manufacture of the composite moldedpart or of the composite fiber molded part without special stabilizationmeasures. In this case it is within the scope of the invention that thelaminate that can already be used as a semifinished product is deliveredto the composite molded part or composite fiber molded part for furtherprocessing without stabilization, in particular without thermalstabilization or without calendering and/or without needling and/orwithout stitching and/or without adhesion and/or without chemicalstabilization. In this case “without stabilization” means in particularthat the laminate or the semifinished product can in principle be easilycompacted or can be easily compacted by compacting rollers, but is notsubjected to any special stabilization method, in particular no thermalstabilization or needling or stitching or adhesion. In this respect theinvention is based on the recognition that a special stabilization isnot necessary if low-melting fibers at the fiber temperature T_(F)according to the invention are combined with the reinforcement materialor with the reinforcement fibers into the laminate or into thesemifinished product.

In principle within the scope of the method according to the inventiondifferent materials are used for the high-melting reinforcementmaterial, for example high-melting reinforcement fibers in the form ofglass fibers or the like. However, the high-melting reinforcementmaterial or the high-melting reinforcement fibers may also be made of aplastic or a thermoplastic plastic. A preferred embodiment of theinvention is characterized in that in the method according to theinvention the high-melting reinforcement material or the high-meltingreinforcement fibers on the one hand and the low-melting fibers on theother hand are made of the same plastic or of the same type of plastic.Thus for example high-melting polypropylene fibers are used asreinforcement fibers and low-melting polypropylene fibers are used aslow-melting fibers for making the semifinished product according to theinvention. Further below and with regard to the same plastic or the sametype of plastic for the high-melting reinforcement material and for thelow-melting fibers further embodiments are disclosed that relate or maybe related to the method according to the invention. Thus within thescope of the method according to the invention for example according tothe invention high-melting polypropylene fibers are used asreinforcement fibers and low-melting polypropylene fibers are used aslow-melting fibers for making the semifinished product according to theinvention.

Advantageously the low-melting fibers or at least a layer of low-meltingfibers is used in the form of a nonwoven fabric or in the form of arandom fiber sheet. It is within the scope of the invention that thelow-melting fibers are produced or spun as continuous filaments. As isexplained in greater detail below, according to a particularlyrecommended embodiment of the invention the low-melting fibers are spunas melt-blown fibers and particularly preferably as biax melt-blownfibers. The low-melting fibers then preferably have a fiber diameterfrom 1 to 10 μm. In principle the low-melting fibers are also producedas a spun-laid nonwoven made of continuous filaments by a spunbondmethod. Also this method is explained in greater detail below. Accordingto another variant the low-melting fibers can also be produced in thecontext of a hot-melt method with the aid of a hot-melt blow head.

A recommended embodiment of the invention is characterized in that thelayer of high-melting reinforcement material—in particular the layer ofhigh-melting reinforcement fibers—is between at least two layers and inparticular between two layers of low-melting fibers of thermoplasticplastic to form the laminate. Thus according to a variant of theinvention a three-layer laminate is produced. In principle in thelaminate produced within the scope of the invention further layers ofreinforcement material/reinforcement fibers and/or of low-melting fibersare possible.

The invention also relates to a method of making a semifinished productfor the manufacture of a composite molded part, in particular acomposite fiber molded part, wherein a high-melting reinforcementmaterial, in particular high-melting reinforcement fibers, is combinedwith low-melting fibers of thermoplastic plastic into a laminate,wherein the low-melting fibers are spun and after spinning are combinedwith the high-melting reinforcement material, in particular with thehigh-melting reinforcement fibers into the laminate forming thesemifinished product, and wherein the high-melting reinforcementmaterial or the high-melting reinforcement fibers and the low-meltingfibers are made of the same plastic or the same type of plastic. Afterspinning, the low-melting fibers are combined at a fiber thickness <10den, preferably <3 den and particularly preferably <1.5 den with thehigh-melting reinforcement material, in particular with the high-meltingreinforcement fibers, into the laminate forming the semifinishedproduct.

According to this embodiment of the invention both the high-meltingreinforcement material or the high-melting reinforcement fibers and alsothe low-melting fibers are made of the same polyolefin or of the samepolyester or of the same polyamide. Thus both the high-meltingreinforcement fibers and also the low-melting fibers are made ofpolypropylene or of polyethylene or of polyethylene terephthalate (PET)or of polybutylene terephthalate (PBT). According to a variant thehigh-melting reinforcement fibers may for example be made ofpolyethylene terephthalate (PET) and the low-melting fibers may be madeof a copolymer of the polyethylene terephthalate (CoPET). In thisrespect “the same type of plastic” also means at least one plastic or acopolymer of the relevant plastic or the same plastic.

In this embodiment with the same plastics or with the same types ofplastic the higher melting point of high-melting reinforcement fiberscan be reached in that the high-melting reinforcement fibers have ahigher crystallinity than the low-melting fibers. The high-meltingreinforcement fibers can be stretched more markedly than the low-meltingfibers. However, the lower melting point of the low-melting fibers canalso be achieved by additions—for example by the addition of a copolymerwith a lower melting point.

Also in the embodiment with the same plastics or with the same types ofplastic the melting point of the high-melting reinforcement material orof the high-melting reinforcement fibers is at least 1° C., preferablyat least 5° C. higher than the melting point of the low-melting fibers.According to a variant the difference between the melting points is atleast 10° C. or at least 20° C.

The embodiment with the same plastic or with the same type of plastic inthe high-melting reinforcement material, on the one hand, and in thelow-melting fibers, on the other hand, is characterized in anadvantageous manner by problem-free recycling. In the recycling of thecomposite molded parts or composite fiber molded parts produced from thesemifinished product according to the invention a costly separation ofthe individual components is not necessary. This is very advantageousespecially for composite molded parts in the automotive industry, sincea high recycling rate is required here. Furthermore in this embodimentthe spun low-melting fibers can be combined in a simple and especiallyeffective manner with the high-melting reinforcement material or withthe high-melting reinforcement fibers, resulting in relatively stablelaminates for which very energy-intensive stabilization measures are notnecessary in principle. It is within the scope of the invention thatalso in the embodiment according to FIG. 6 with the same plastics or thesame types of plastic the semifinished product is delivered to thecomposite molded part, in particular to the composite fiber molded part,for further processing without stabilization, in particular withoutcalendering and/or without needling and/or without stitching and/orwithout adhesion and/or without chemical stabilization.

Nevertheless it is, however, also within the scope of the invention thatin this embodiment the laminate consisting of the at least one layer ofhigh-melting reinforcement material—in particular of high-meltingreinforcement fibers—and the at least one layer of low-melting fibers isstabilized before the further processing into the composite molded partor the composite fiber molded part. In this case “stabilization of thelaminate” means in particular the connection and/or the entanglement ofthe high-melting and low-melting components. The laminate is preferablystabilized by at least one type of stabilization from the group“mechanical needling, water jet stabilization, calendering,thermobonding with hot air, adhesion, chemical connection.” “Adhesion”here means in particular adhesion by hot-melt, in particular from thesame group of substances as the reinforcement material and thelow-melting fibers. Because of the additional stabilization the laminateis particularly easy to handle and is characterized by good drapingproperties, so that the laminate can also be used without problems asmaterial on a roll.

The preferred embodiments or variants explained below relate both to theteaching according to the invention as set forth in the invention withthe same plastic or with the same type of plastic for the high-meltingcomponent and the low-melting component.

An embodiment that is particularly important within the scope of theinvention is characterized in that the at least one layer of low-meltingfibers of thermoplastic plastic is a nonwoven fabric. It is within thescope of the invention that the nonwoven fabric is a random fiber sheet.In the laminate according to the invention all layers are advantageouslymade of low-melting fibers of thermoplastic plastic nonwoven fabrics.According to a particularly recommended embodiment of the invention anonwoven fabric made of low-melting fibers is a spun-laid nonwoven madeof continuous filaments.

It is within the scope of the invention that such a spun-laid nonwovenis produced from continuous filaments by a spunbond method. In this casecontinuous filaments of thermoplastic plastic are spun from a spinneretand are then cooled in a cooling chamber. These cooled continuousfilaments are then advantageously introduced into a stretching unit andfinally are preferably set down on a conveyor belt or screen belt. It isrecommended that the continuous filaments of the spun-laid nonwoven havea fiber diameter of 10 to 35 μm, and preferably the fiber diameter ofthe continuous filaments is greater than 10 μm or significantly greaterthan 10 μm. The melt flow index (MFI) of the polypropylene used for themanufacture of a spun-laid nonwoven is advantageously 10 to 100 g/10min. Within the scope of the invention the melt flow index (MFI) ismeasured according to EN ISO 1133 at a test temperature of 230° C. andat a nominal mass of 2.16 kg. According to a preferred embodiment of theinvention a layer made of high-melting reinforcement material—inparticular of high-melting reinforcement fibers—is between two spun-laidnonwovens made of continuous filaments of thermoplastic plastic.

A particularly preferred embodiment in the context of the methodaccording to the invention is characterized in that a melt-blownnonwoven is used as nonwoven fabric and preferably a biax melt-blownnonwoven is used. Melt-blown nonwovens and especially biax melt-blownnonwovens have proved particularly successful within the scope of theinvention. Melt-blown nonwovens are produced in melt-blown machines thathave a nozzle head or melt-blown blow head that is equipped with aplurality of nozzle orifices arrayed in at least one row. From thesenozzle orifices the plastic melt or the molten plastic filaments is/areextruded into a very fast blow air stream. As a result the melt istransformed into fine fibers, solidified, and the fibers are then setdown on a support, in particular on a screen belt—to form a fine-fibermelt-blown nonwoven. In the conventional melt-blown method an extensiveblow air stream or extensive blow air streams is/are applied to thecurtain of extruded plastic filaments from the side or from oppositesides. In contrast to this, in the biax melt-blown method a separateblow air stream or a blow air stream surrounding the filament like asheath is applied to each individual nozzle orifice or each individualextruded plastic filament. Biax melt-blown nonwovens produced by thebiax melt-blown method have proved particularly successful within thescope of the invention. The melt-blown nonwovens or biax melt-blownnonwovens used in the method according to the invention have fibers witha fiber diameter of advantageously 1 to 10 μm. A polypropylene with amelt flow index (MFI) of 75 to 2,500 g/10 min is used for example formaking the melt-blown nonwovens or biax melt-blown nonwovens. A meltflow index of 100 to 150 g/10 min has provided quite particularlysuccessful. According to a particularly recommended embodiment of themethod according to the invention a layer made of high-meltingreinforcement material or of high-melting reinforcement fibers is usedthat is between or directly between two melt-blown nonwovens andpreferably between two biax melt-blown nonwovens. In principle in thisembodiment, with the same plastics or the same types of plastic, thelow-melting fibers can also be produced in the context of a hot-meltmethod with the aid of a hot-melt blow head.

According to an embodiment of the method according to the invention thathas proved successful, low-melting fibers of at least one polyolefin,preferably of polypropylene and/or polyethylene, are used. However, inprinciple the low-melting fibers can also be made of otherthermoplastics, in particular also of a polyester, for example ofpolyethylene terephthalate (PET) or of polyamide (PA).

It is recommended that for a layer made of high-melting reinforcementfibers at least one fiber type from the group “glass fibers, aramidfibers, carbon fibers, metal fibers, fibers of thermoplastic plastic” isused. In principle the high-melting reinforcement fibers may also benatural fibers. The fibers can be used as short fibers and/or longfibers. It is within the context of the invention that the layer ofhigh-melting reinforcement fibers is a laid fabric and/or a woven fabricand/or a braided fabric and/or a knitted fabric. Laid fabrics and wovenfabrics have proved particularly successful. Thus for example a laidfabric of glass fibers can be used as a layer of high-meltingreinforcement fibers. According to another preferred embodiment of theinvention the layer of high-melting reinforcement fibers is a nonwovenfabric of high-melting reinforcement fibers, preferably of high-meltingplastic fibers. Thus for example a nonwoven fabric of PET fibers can beused as a layer of high-melting reinforcement fibers, wherein thisnonwoven fabric is for example between two melt-blown nonwovens made ofpolypropylene fibers. Moreover it has proved successful for thereinforcement fibers to be admixed with an impregnating agent or with anadhesion promoter in order to achieve a better contact or adhesion withthe molten thermoplastic plastic.

According to a variant the at least one layer of reinforcement fibers asmaterial on a roll is combined with the at least one layer oflow-melting fibers or the reinforcement fibers are for example combinedin an air-laid method with the at least one layer of low-melting fibers.The at least two layers can also be applied to one another continuouslyas material on a roll or discontinuously as two-dimensional sheetmaterials. It is within the scope of the invention that the laminateproduced according to the invention can be rolled up into a roll andthus can be further used as material on a roll. This is made possible bythe flexible characteristics and by the good draping properties of thelaminate produced according to the invention.

The manufacture of a composite molded part, in particular a compositefiber molded part, according to the invention is described below. In thecomposite molded part or composite fiber molded part, high-meltingreinforcement material or high-melting reinforcement fibers is embeddedin a matrix of thermoplastic plastic. For making the composite moldedpart or of the composite fiber molded part heat and/or pressure isapplied to the laminate or the semifinished product produced accordingto the invention, so that the low-melting fibers of thermoplasticplastic melt and the non-molten reinforcement material or the non-moltenreinforcement fibers are impregnated with the thermoplastic melt or areembedded in the matrix of thermoplastic plastic. The application of heatand/or pressure to the laminate or to the semifinished product can takeplace “inline” or “offline.” It is within the scope of the inventionthat when heat and/or pressure are applied the heating temperature isselected or adjusted so that only the low-melting fibers melt or thatsubstantially only the low-melting fibers melt. It will be understoodthat, after the application of heat and/or pressure or after the moldingof the composite molded part/composite fiber molded part, a cooling ofthe matrix of thermoplastic plastic with the embedded reinforcementmaterial or with the embedded reinforcement fibers takes place. With themethod according to the invention a composite molded part or compositefiber molded part is preferably produced as a lightweight construction.

For the application of warmth or heat and/or pressure the laminate orthe semifinished product produced according to the invention isadvantageously introduced into a pressing tool and is preferablydeformed there under the effect of heat and the effect of pressure. Theimpregnation of the reinforcement material or the reinforcement fiberswith the thermoplastic melt and the embedding of the reinforcementmaterial or of the reinforcement fibers in the matrix of thermoplasticplastic should take place within the scope of the invention ascompletely as possible and with minimization of air inclusions.

A quite particularly preferred embodiment of the method according to theinvention is characterized in that the laminate/semifinished productproduced according to the invention is transformed into a compositemolded part or composite fiber molded part by application of heat and/orpressure directly in the course of a thermoforming process and/or aninjection-molding process. Thus, in contrast to the method known in theart as described in the introduction, the laminate/semifinished productis then processed to form the end product directly and without anintermediate melting and hardening process. Thus there is no need forthe manufacture of an additional semifinished product from thereinforcement material or from the reinforcement fibers and athermoplastic matrix and therefore by comparison with the known method aprocessing step can be omitted. “Thermoforming process” means inparticular a deep-drawing process. In the preferred embodiment describedabove the laminate/semifinished product produced according to theinvention can therefore be directly deep-drawn. Because of the ease ofhandling and good draping properties of the laminate/semifinishedproduct, three-dimensional or multi-dimensional molded parts can beproduced according to the invention without problems.

According to another embodiment of the method according to the inventionheat and/or pressure is applied to the laminate/semifinished product ina first step and a further or second semifinished product is formed witha matrix of thermoplastic plastic and reinforcement material embeddedtherein or reinforcement fibers embedded therein. This further or secondsemifinished product of thermoplastic matrix and embedded reinforcementmaterial or embedded reinforcement fibers is then transformed, onlylater or in a second step, into a composite molded part or a compositefiber molded part by application of heat and/or pressure in the courseof a thermoforming process and/or an injection-molding process. Thushere, as in the method known in the art, first of all in an additionalstep a further semifinished product is produced that is then processedlater to form the end product, for example by deep-drawing to form athree-dimensional or multi-dimensional molded part. Advantageously thefurther or second semifinished product is produced from thethermoplastic matrix and the embedded reinforcement material in theshape of plates.

The invention also relates to a method of making a composite moldedpart, in particular a composite fiber molded part, with reinforcementmaterial or reinforcement fibers embedded in a matrix of thermoplasticplastic, wherein at least one layer of high-melting reinforcementmaterial—in particular of high-melting reinforcement fibers—is combinedwith at least one layer of low-melting fibers of thermoplastic plasticinto a laminate. The laminate forms the semifinished product from whichthe composite molded part or composite fiber molded part can beproduced. A distinction is made between the first semifinished product(laminate) described here and the optional further or secondsemifinished product (semifinished product made of thermoplastic matrixwith embedded reinforcement material) described above. The invention isbased on the recognition that the semifinished product in the form ofthe laminate is relatively simple to handle and especially because ofits good draping properties it can be wound onto rolls and can be usedas material on a roll. In particular a laminate with at least onemelt-blown nonwoven as low-melting component can often be handledwithout problems without additional stabilization because of goodadhesion and can be further processed to form the composite moldedpart/composite fiber molded part directly or for example can be woundonto a roll.

The invention also relates to a composite molded part, in particular acomposite fiber molded part that can be produced by the method accordingto the invention as described above and/or from the semifinished productaccording to the invention as described above, wherein a high-meltingreinforcement material—in particular high-melting reinforcementfibers—is/are embedded in a matrix of low-melting thermoplastic plasticand wherein the matrix has been produced from low-melting fibers of thethermoplastic plastic.

The invention is based first of all on the recognition that thesemifinished products produced by the method according to the inventionare characterized by a particularly effective or firm connection of thelayers forming them. These semifinished products constitute surprisinglydimensionally stable assemblies that can be further processed or furtherhandled without further stabilization or at least withoutenergy-intensive stabilization measures. The laminates or semifinishedproducts produced according to the invention are characterized byexcellent handling and in particular draping properties. Thesemifinished products can advantageously be processed directly to formthe composite molded part or the composite fiber molded part or can bewound directly on rollers. In this respect the invention ischaracterized by low complexity and low costs. The semifinished productscan be used without problems as flexible material on a roll andthree-dimensional or multi-dimensional molded parts can be produced in asimple manner. Furthermore the invention is based on the recognitionthat when the measures according to the invention are implemented anoptimal impregnation or wetting of the reinforcement fiber with the meltof thermoplastic plastic is possible. Air inclusions in thethermoplastic matrix can be avoided or at least largely avoided. In themethod according to the invention the impregnation or wetting and theformation of the molded parts can take place in a simple manner in asingle pressing tool. The composite molded parts or composite fibermolded parts produced according to the invention are also characterizedby outstanding mechanical characteristics. Furthermore it may be pointedout that in particular with appropriate choice of material the compositemolded parts or composite fiber molded parts produced according to theinvention can be recycled in a simple and inexpensive manner. In thisrespect the invention is characterized by low complexity and low costs.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described in greater detail below with reference todrawings that show only one embodiment. In the drawings, in schematicrepresentation:

FIG. 1 shows schematically the manufacture of a laminate forming asemifinished product according to the invention,

FIG. 2 shows a device for carrying out the method according to theinvention,

FIG. 3 is a section through a composite fiber molded part producedaccording to the invention, and

FIG. 4 is a perspective view of a composite fiber molded part producedaccording to the invention.

SPECIFIC DESCRIPTION OF THE INVENTION

FIG. 1 schematically shows the manufacture of a laminate 4 forming asemifinished product according to the invention. The laminate 4 hereconsists of a layer of high-melting reinforcement fibers in the form ofa glass-fiber fabric 5 made of glass fibers 8. Low-melting fibers 10 arepreferably produced in this embodiment by a biax melt-blown method.These fibers may be low-melting polypropylene fibers that are combinedwith the glass fibers 8 or with the glass-fiber fabric 5. Advantageouslyin this embodiment a biax melt-blown nonwoven 6 is laid on theglass-fiber fabric 5. According to the invention the low-melting fibers10 or the polypropylene fibers have a fiber temperature T_(F) in theregion of the heat-distortion temperature T_(W) of the polypropylene. Itcan be seen from FIG. 1 that because of their fiber temperature T_(F)the low-melting fibers 10 combined with the glass fibers 8 or with theglass-fiber fabric 5 are so soft or flexible and malleable that theypenetrate with fiber sections 11 into interstices 12 formed between theglass fibers 8 of the glass-fiber fabric 5. In this way an effectiveentanglement or connection between the high-melting glass fibers 8 andthe low-melting fibers 10 is produced. The laminate 4 that is formed canin principle be supplied without special stabilization for furtherprocessing to form the composite molded part or the composite fibermolded part 7.

FIG. 2 shows very schematically a pressing tool 1 with two platens 2 and3. In the embodiment a three-layer laminate 4 is between the platens 2and 3. This laminate 4 has a central layer of high-melting reinforcementfibers in the form of a glass-fiber fabric 5. This glass-fiber fabric 5is between two biax melt-blown nonwovens 6 made of polypropylene fibers.When the platens 2 and 3 are pressed together, heat and pressure appliedto the laminate melt the low-melting polypropylene fibers. The heatingtemperature is selected so that only the polypropylene fibers melt andthe glass fibers 8 of the glass-fiber fabric 5 on the other hand are notmelted. On the contrary, the glass fibers 8 are impregnated or wetted bythe thermoplastic polypropylene melt and in this way the glass fibers 8are embedded in a matrix of thermoplastic plastic (PP). According to apreferred embodiment of the invention a composite fiber molded part 7can be produced directly in the manner described above. A simplepressing tool 1 is shown only very schematically in FIG. 2. In principlewithin the scope of the invention three-dimensional or multi-dimensionalmolded parts with complicated structures can be produced in a simplemanner with special pressing tools. The flexible handling and gooddraping properties of the laminate 4 contribute to this.

FIG. 3 shows a section through a composite fiber molded part 7 producedby the method according to the invention after cooling. It can be seenthat the glass fibers 8 of the glass-fiber fabric 5 are completelyembedded in the thermoplastic polypropylene matrix. Disruptive airinclusions are not observed and they can be avoided in a simple mannerwhen the measures according to the invention are implemented. Thecomposite fiber molded parts 7 produced in this way according to theinvention have optimal mechanical characteristics. In FIG. 4 moreover afurther composite fiber molded part 7 with multi-dimensional structureproduced according to the invention is illustrated. Within the scope ofthe method according to the invention multi-dimensional structures canbe implemented simply and without problems.

We claim:
 1. A method of making a semifinished product for the manufacture of a composite fiber molded part, the method comprising the steps of: a) spinning from a row of orifices of a spinning nozzle low-melting fibers of a thermoplastic; and b) combining the spun low-melting plastic fibers into a laminated semifinished product with high-melting reinforcement fibers of the same thermoplastic but having a melting temperature higher than the melting temperature of the low-melting fibers.
 2. The method defined in claim 1, further comprising the step of: consolidating the semifinished product by mechanical needling, water-jet stabilization, calendering, thermobonding with hot air, adhesion, or chemical bonding.
 3. The method defined in claim 1, further comprising the step after step b) of: c) applying heat or pressure to the semifinished product such that the low-melting fibers melt and form a thermoplastic material that impregnates the reinforcement fibers and forms a matrix in which the reinforcement fibers are embedded; and thereafter d) forming the laminate into a molded body.
 4. The method defined in claim 1, further comprising the step, after step a) and before step (b) of: a″) forming the low-melting fibers into a nonwoven.
 5. The method defined in claim 1, wherein the low-melting fibers are spun as continuous filaments in step a).
 6. The method defined in claim 1, wherein the low-melting fibers are formed as meltblown fibers.
 7. The method defined in claim 6 wherein the meltblown fibers are biaxial.
 8. The method defined in claim 1, wherein the high-melting fibers have a melting temperature at least 1° higher than a melting temperature of the low-melting fibers.
 9. The method defined in claim 8, wherein the melting temperature of the high-melting fibers is at least 5° higher than the melting temperature of the low-melting fibers.
 10. The method defined in claim 1, further comprising the steps of: a′) forming the low-melting fibers of step a) into two layers before step b), and b′) sandwiching the high-melting fibers between the layers.
 11. The method defined in claim 1, further comprising the step of: c) applying heat or pressure to the semifinished product such that the low-melting fibers melt and form a thermoplastic material that impregnates the reinforcement fibers and forms a matrix in which the reinforcement fibers are embedded.
 12. The method defined in claim 11, wherein after step c) the laminate is thermoformed into a finished product. 